Linear rheostat



Sept. 12, 1967 w. P. LEAR I LINEAR RHEOSTAT Filed Dec. 2, 1963 United States Patent 3,341,800 LINEAR RHEOSTAT William P. Lear, Wichita, Kans, assignor to Lear Jet Industries, Inc, a corporation of Delaware Filed Dec. 2, 1963, Ser. No. 327,389 2 Claims. (Cl. 338183) This invention relates to rheostat or potentiometer means, and more specifically to linear rheostat means. In a more specific aspect the invention relates to new linear rheostat means which are constructed and adapted so that same can be manufactured in standard sizes, and made into any convenient length by the purchaser simply by cutting to the desired length. In a still more specific aspect the invention relates to a linear rheostat or potentiometer which has switch means associated therewith so that the potentiometer or rheostat can be mounted on and driven by a linear actuator or the like with the rheostat or potentiometer providing an electrical follow up or feedback signal and with the switch means providing means for limiting movement of the actuator.

Various rheostat or potentiometer means are known to the art whereby a variable resistance can be obtained for a particular circuit. Some prior art rheostat or potentiometer means are structurally relatively complicated and therefore expensive to manufacture and sell. In addition, the prior art linear rheostats or potentiometers are normally available only in specific predetermined lengths and there is little flexibility for a particular rheostat. Some of the prior art potentiometers or rheostats are not adapted to be used with linear actuating means so that the rheostat can provide a follow up or feedback signal. Furthermore, means for limiting movement of an associated linear actuator is not normally provided with prior art rheostats and is quite desirable in preventing damage to the actuator.

In accordance with the present invention rheostat means are provided which include a form and wire =means positioned on the form. The wire means desirably has insulation means thereon and a portion of the insulation means can be removed to provide a contact surface or area. Conductor means are electrically insulated from the contact surface of the wire means and contact means are provided having spaced portions engagable with the conductor means and the contact surface or area of the wire means. Means are operatively connected to the contact means for movably mounting the contact means relative to the wire means and the conductor means.

Accordingly, it is an object of the invention to provide new rheostat or potentiometer means.

A further object of the invention is to provide new linear rheostat or potentiometer means which is relatively inexpensive and simple to manufacture.

Another object of the invention is to provide a linear rheostat or the like which can be made in any convenient length simply by cutting it ofr to the desired length and attaching suitable fitting members.

A still further object of the invention is to provide a new linear rheostat or potentiometer which incorporates in one device a linear potentiometer with limit switch means so that the potentiometer or rheostat can be mounted on and driven by a linear actuator or similar device with the potentiometer or rheostat providing an electrical follow up or feedback signal and with the limit switch means limiting movement of the actuator.

Various other objects, advantages, and features of the invention will become apparent to those skilled in the art from the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a transverse cross section view of a preferred specific embodiment of the invention taken along the line 1-1 of FIG. 2 and looking in the direction of the arrows.

FIG. 2 is a longitudinal cross section view taken along the line 22 of FIG. 1.

FIG. 3 is an end view of the rheostat of FIGS. 1 and 2.

FIG. 4 is an enlarged partial transverse cross section view of the rheostat of FIGS. 1-3.

FIG. 5 is an enlarged view, partially broken away, of a portion of the rheostat of the invention.

The following is a discussion and description of a preferred specific embodiment of the new linear rheostat or potentiometer of the invention, such being made with reference to the drawings whereon the same reference numerals are used to indicate the same or similar parts and/ or structure. It is to be understood that such discussion and description is not to unduly limit the scope of the invention.

Referring now to the drawings in detail, a preferred specific embodiment of the linear rheostat or potentiometer of the invention is shown generally at 10 and desirably includes two side members 12 and 14 which preferably are of like construction and are positioned in mirror image relation as best illustrated in FIG. 1. The side members 12 and 14 each desirably have an elongated base portion as shown at 16 and 18 and the base portions preferably project laterally from the side members and can be located at lower edge portions thereof as illustrated in the drawings. The base portions 16 and 18 preferably have the outermost edges thereof positioned in engagement as shown in FIGS. 1 and 4 and the other portions of the side members 12 and 14 are desirably located in spaced relation to each other as shown. Suitable mounting means, such as bolts or the like 20 can be passed through the base portions 16 and 18 of side members 12 and 14 to thereby connect the side members together. The base portions can, if desired, be separately formed members and connected to the side members by the bolts 20.

The side member 12 has two spaced longitudinally extending ribs or projections 22 and 24 on the inner surface thereof which are located in spaced relation to the base portion 16 and desirably are generally parallel to the base portion 16. In the same manner the side member 14 has projections 26 and 28 on the inner surfaces thereof in spaced relation to base portion 18. The base portions 16 and 18 and the projections 24 and 28 on side members 12 and 14 together define a generally channel shaped recess 30 at the lower portion of the side members and the projections 22, 24, 26 and 28 together define two opposed guides or slots in the side members to receive a slider member as explained hereinafter.

Positioned within the channel shaped recess 30 is an insulator 32 which is preferably a soft plastic material or other suitable insulating means. The insulator 32 can be preformed or shaped and positioned within the recess 30 or it can be sheet stock or the like and applied to the walls of the side members forming the recess 30. The insulator 32 preferably substantially covers the walls of the recess 30 and can have edge portions projecting inwardly toward each other as best illustrated in FIG. 5 to thereby cover the lower surfaces of the projections 01' ribs. 24 and 28 of the side members. An additional insulator strip or member 34 can be provided, if desired,

and positioned within the insulator 32 and such can be a strip of any suitable insulation material.

An elongated channel shaped electrical conductor 36 is mounted within the insulator strips 34 and 32 and the conductor 36 preferably has edge portions 38 and 40 projecting inwardly toward each other at the open side of the channel shaped conductor. The conductor 36 can be a silver band or can be constructed from other suitable conducting and non-tarnishing metals. The insulator or strip 34 can be connected to the conductor if desired.

Positioned within the conductor 36 is a resistance member which is shown generally at 42. The resistance member preferably includes an elongated form 44 which can be of rectangular cross section as illustrated in the drawings and can be constructed of wood, plastic or other materials and preferably is of a non-conducting material. A continuous length of wire 46 is wound in a helical manner on the form 44 and preferably adjacent convolutions of the wire are in engagement with each other. The Wire member 46 preferably includes an electrical conductor or wire 48 covered by a non-conducting insulation 50 and the insulation 50 can be an enamel coating or other suitable insulation. The resistance member 42 is positioned within and substantially fills the space within the conductor 36 and the wire 48 is electrically insulated from the conductor 36 by the insulation 50.

At least the upper portion of the insulation 50 on wire 46 is removed from each convolution of the wire 46 to provide an elongated contact area or surface 52 between the edge portions 58 and 40 of conductor 36. As will be apparent from FIG. 5, the contact area 52 is spaced from the edges of the conductor 36 and insulated therefrom by the insulation 56 of the wire 46. The contact area 52 can be formed by buffing or otherwise removing a portion of the insulation 50 on wire 46 after the wire has been wound on form 44.

An elongated slide or slider 56 is positioned between the side members 12 and 14 and the slide 56 preferably has ribs or the like 58 and 69 projecting from opposite sides thereof which are slidably positioned in the guides formed by the projections 22, 24, 26 and 28 on the side members 12 and 14. The slider 56 is movable along the guides of the side members and to facilitate movement of the slider it can be formed of a suitable antifriction material, such as flurocarbon materials including polytetrafiuroethylene and trichlorofiuroethylene, or other suitable plastics can be used including nylon or the like. The slide 56 preferably has a hole 62 extending longitudinally therethrough and an elongated rod or the like 64 is positioned in the hole 62 and extends from both ends of the slide and the rod is desirably connected to the slide so that movement of the rod causes movement of the slide. The rod or the like 64 can be connected to or be a part of a linear actuator mechanism (not shown) so that movement of the rod by the associated mechanism causes movement of the slider 56.

The lower portion of the slide 56 is positioned adjacent the channel shaped recess 30 and a contact member 66 is connected to the lower surface of the slider 56. The

I contact member 66 preferably has three spaced finger like contacts 68, 70 and 72 on the lower surface thereof and the contact portions 68 and 72 slidably engage the edge portions 38 and 40, respectively of the conductor 36 and the contact portion 70 slidably engages the contact surface or area 52 formed from the wire 46. By connecting the conductor 36 and the wire 46 in an electrical circuit and by movement of the slider 56 and contact member 66 relative to the side members 12 and 14, the total resistance of the circuit can be varied as a result of the electrical contact between the finger like contacts of the member 66 and the conductor 36 and the contact 52. The member 66 can be made of any suitable electrically conducting material, such as a phosphor bronze, silver plated spring brass or other suitable material. When the rod 64 is connected to a linear actuator or other mechanism for moving same the potentiometer or rheostat means of the invention provides a follow up or feedback signal in association with and as a direct result of movement of the actuator.

Two end plates 76 and 78 are preferably provided and are connected to the side members 12 and 14 at opposite ends thereof as illustrated in FIG. 2. The end plates 76 and 78 are preferably generally T-shaped as best illustrated in FIG. 3 with the wide portion thereof being positioned over the upper edges of the side plate and the end plates have holes therethrough to slidably receive the rod 64. End plate 76 preferably has a plurality of pins or the like 80 projecting therethrough and the inner ends of the pins form lugs and can be electrically connected to the electrical elements within the rheostat, such as the conductor 36, the wire 46 and the switch means described hereinafter. The outer ends of the pins can be used for connecting the electrical elements in an electrical circuit.

Switch means are preferably provided with the rheostat 10 so that when the rod 64 is connected to or forms a part of a linear actuator or the like the switch means can be connected to the actuator to limit movement of the actuator and thus prevent damage to the actuator. As shown in the drawings, the switch means include two micro switches 82 and 84 which are positioned between the side members 12 and 14 at opposite ends thereof in spaced relation to the projection 22 and 26 and desirably the switch means 82 and 84 are located adjacent the end plates 76 and 78. Switch 82 has a switch operator 86 projecting from the lower surface thereof and switch 84 has a similar operator 88 at the lower surface thereof. The switch operators 86 and 88 are engageable by the upper portion of the slide 56 so that when rod 64 is moved the slide can engage the switch operators 86 and 88 and operate the switches 82 and 84 to open and close same and thus limit travel of the rod and the associated actuator mechanism.

An elongated, generally channel shaped cover 90 can be provided and the leg or outer edge portions thereof can be secured to the side portions 12 and 14 by suitable bolt means or the like 9 2 and the bolt means 92 can also be used for mounting of the micro switches '82 and 84 if desired.

In operation, the rod 64 is moved by any suitable means to cause movement of the slider 56 and the contact member 66 so that the portions 68, 70 and 72 of the contact member are moved along and in engagement with the edges of the conductor 36 and the contact area 52 of the resistor member so that when the conductor and resistor member are connected in an electrical circuit the resistance of the circuit is variable as a result of movement of the slider. When switches 82 and 184 are provided and rod 64 is moved by a linear actuator, movement or travel of the slider and the associated linear actuator can be limited by operation of the switches as a result of engagement of the switch operators 86 and 88 by the slider.

The linear rheostat of the invention can be manufactured in any suitable length and cut to size for use merely by cutting the side members 12 and 14, the resistor member 42 and conductor 36 and associated parts so that the desired total resistance can be obtained. When these elements have been cut to length the various parts can be assembled as shown in the drawings and the end plates can be attached.

Legs or mounting brackets 94 can be mounted on the side members 12 and 14 at the lower portion thereof by the use of the bolts 20 and the legs or brackets 4 can be used to support the rheostat or mount same on a linear actuator or other mechanism. The electrical connection between the rheostat and the associated circuit can be quickly made through the pins 80.

In manufacturing the rheostat and parts thereof, the side members 12 and 14 can be extruded or machined and since they are the mirror image of each other such can be made in a very long length and cut to the desired length. Also, the structure illustrated in FIG. 5 of the drawings can be made in a unit and cut to the desired size prior to assembly. By making the various parts so that they can be stocked in standard lengths and cut to size manufacturing economies are obtained which are not normally realized with prior art structures.

While the rheostat of the invention has been described in connection with a preferred specific embodiment thereof, it will be apparent to those skilled in the art that various modifications or changes can be made without departing from the invention as defined in the claims.

I claim:

-1. A linear rheostat comprising, in combination, two elongated side members of like construction positioned in mirror image relation, said side members each having an elongated laterally projecting base portion at a longitudinal edge portion thereof, the outermost edges of said base portions of said side members being in engagement and the other portions of said side members being located in spaced relation, mounting means connecting said outermost edges of said base portions of said side members together, said side members each having two spaced longitudinally extending projections located in spaced relation to said base portions with said projections defining therebetween opposed guides and with said base portions of said side members and the adjacent ones of said projections defining therebetween a channel shaped recess, an insulator of soft plastic material positioned in said recess and substantially covering the walls of said recess, an elongated channel shaped electrical conductor mounted in said recess and within said insulator with said conductor having edge portions projecting inwardly toward each other, a resistance member including an elongated form of rectangular cross section and a continuous length of wire having an insulated coating thereon with said wire being wound on said form vfrom one end portion thereof to the other end portion thereof, said resistance member being positioned within and substantially filling the space within said conductor with said wire being insulated from said conductor by said coating on said wire, a portion of each convolution of said wire between said edge portions of said conductor having the insulation coating removed therefrom to form an elongated contact area, an elongated slide positioned between said side members and having ribs projecting from each side thereof and slidably positioned in said guides of said side members to thereby movably mount said slide in said side members, an elongated rod attached with said slide and projecting from both ends thereof, said slide having a portion thereof positioned adjacent and in spaced relation to said conductor and said resistance member in said channel shaped recess, a contact member connected to said portion of said slide and having spaced finger like contacts slidably engaging portions of said conductor and said contact area of said resistance member in said channel shaped recess, and two end plates connected to said side members at opposite ends thereof, each of said end plates having an opening therethrough slidably receiving said rod.

2. A linear rheostat, comprising, in combination, two elongated side members of like construction positioned in mirror image relation, said side members being connected together at base portions thereof and having portions projecting toward each other and defining a substantially channel shaped recess and opposed guides, an elongated generally channel shaped electrical conductor positioned in said recess and having edge portions projecting inwardly toward each other, an elongated resistance member including a form and a length of wire wound about said form, said wire being insulated and having a linear region of the insulation removed to provide a contact area, said resistance member being positioned within said conductor with said contact area being positioned between and spaced from said edge portions of said conductor, a slide positioned between said side members and having portions thereof slidably mounted in said guides of said side members, means connected to said slide to move same, a contact member connected to said slide and having contact portions slidably engaging portions of said conductor and said contact area of said wire of said resistance member, said rheostat being constructed and adapted so that said conductor and said wire can be connected in an electrical circuit and said slide moved relative to said conductor and said wire with said contact member in contact therewith to thereby vary the total resistance in the circuit.

References Cited UNITED STATES PATENTS 1,880,239 10/1932 Crouse 338183 X 2,526,062 10/1950 Booth 338178 3,124,780 3/1964 H-ulbert 338183 X RICHARD M. WOOD, Primary Examiner.

J. G. SMITH, Assistant Examiner. 

1. A LINEAR RHEOSTAT COMPRISING, IN COMBINATION, TWO ELONGATED SIDE MEMBERS OF LIKE CONSTRUCTION POSITIONED IN MIRROR IMAGE RELATION, SAID SIDE MEMBERS EACH HAVING AN ELONGATED LATERALLY PROJECTING BASE PORTION AT A LONGITUDINAL EDGE PORTION THEREOF, THE OUTERMOST EDGES OF SAID BASE PORTIONS OF SAID SIDE MEMBERS BEING IN ENGAGEMENT AND THE OTHER PORTIONS OF SAID SIDE MEMBERS BEING LOCATED IN SPACED RELATION, MOUNTING MEANS CONNECTING SAID OUTERMOST EDGES OF SAID BASE PORTIONS OF SAID SIDE MEMBERS TOGETHER, SAID SIDE MEMBERS EACH HAVING TWO SPACED LONGITUDINALLY EXTENDING PROJECTIONS LOCATED IN SPACED RELATION TO SAID BASE PORTIONS WITH SAID PROJECTIONS DEFINING THEREBETWEEN OPPOSED GUIDES AND WITH SAID BASE PORTIONS OF SAID SIDE MEMBERS AND THE ADJACENT ONES OF SAID PROJECTIONS DEFINING THEREBETWEEN A CHANNEL SHAPED RECESS, AN INSULATOR OF SOFT PLASTIC MATERIAL POSITIONED IN SAID RECESS AND SUBSTANTIALLY COVERING THE WALLS OF SAID RECESS, AN ELONGATED CHANNEL SHAPED ELECTRICAL CONDUCTOR MOUNTED IN SAID RECESS AND WITHIN SAID INSULATOR WITH SAID CONDUCTOR HAVING EDGE PORTIONS PROJECTING INWARDLY TOWARD EACH OTHER, A RESISTANCE MEMBER INCLUDING AN ELONGATED FORM OF RECTANGULAR CROSS SECTION AND A CONTINUOUS LENGTH OF WIRE HAVING AN INSULATED COATING THEREON WITH SAID WIRE BEING WOUND ON SAID FORM FROM ONE END PORTION THEREOF TO THE OTHER END PORTION THEREOF, SAID RESISTANCE MEMBER BEING POSITIONED WITHIN AND SUBSTANTIALLY FILLING THE SPACE WITHIN SAID CONDUCTOR WITH SAID WIRE BEING INSULATED FROM SAID CONDUCTOR BY SAID COATING ON SAID WIRE, A PORTION OF EACH CONVOLUTION OF SAID WIRE BETWEEN SAID EDGE PORTIONS OF SAID CONDUCTOR HAVING THE INSULATION COATING REMOVED THEREFROM TO FORM AN ELONGATED CONTACT AREA, AN ELONGATED SLIDE POSITIONED BETWEEN SAID SIDE MEMBERS AND HAVING 